Cross sectional depth composition generation utilizing scanning electron microscopy

ABSTRACT

A method for generating cross-sectional profiles using a scanning electron microscope (SEM) includes scanning a sample with an electron beam to gather an energy-dispersive X-ray spectroscopy (EDS) spectrum for an energy level to determine element composition across an area of interest. A mesh is generated to locate positions where a depth profile will be taken. EDS spectra are gathered for energy levels at mesh locations. A number of layers of the sample are determined by distinguishing differences in chemical composition between depths as beam energies are stepped through. A depth profile is generated for the area of interest by compiling the number of layers and the element composition across the mesh.

BACKGROUND

Technical Field

The present invention relates to characterizing layers of an object, andmore particularly to systems and methods for generating cross-sectionalcomposition and structural information using a scanning electronmicroscope (SEM).

Description of the Related Art

A scanning electron microscope (SEM) produces images of a sample orspecimen by scanning with a focused beam of electrons. The electronsinteract with atoms in the sample and produce signals that includeinformation about a sample's surface topography and composition. Anelectron beam is scanned, and its position is combined with a detectedsignal to produce an image. SEM can achieve resolutions of better than 1nanometer.

The electron beam may have an energy ranging from 0.2 keV to 40 keV andis focused by one or more condenser lenses. The beam scans in a rasterpattern over an area of a sample. SEM can provide several items of dataat each pixel. One example includes energy-dispersive X-ray spectroscopy(EDS). An EDS detector may be employed for elemental analysis to analyzean intensity and spectrum of electron-induced luminescence in specimens.The spectra signals can be color coded, so that differences in thedistribution of the various components of the specimen can be seenclearly and compared.

In many applications, specimens are cross-sectioned to determineconstituent structures and materials. In many instances, the specimensto be cross-sectioned are too fragile or too small to deconstruct orcross-section, or the specimens need to be preserved for other analyseswhere non-destructive testing is needed.

SUMMARY

A method for generating cross-sectional profiles using a scanningelectron microscope (SEM) includes scanning a sample with an electronbeam to gather an energy-dispersive X-ray spectroscopy (EDS) spectrumfor at least one energy level to determine element composition across anarea of interest. A mesh is generated to locate positions where a depthprofile will be taken. EDS spectra is gathered for a plurality of energylevels at a plurality of mesh locations. A number of layers isdetermined by distinguishing differences in chemical composition betweendepths as beam energies are stepped through. A depth profile isgenerated for the area of interest by compiling the number of layers andthe element composition across the mesh.

Another method for generating cross-sectional profiles using a SEMincludes scanning a sample with an electron beam to gather an EDSspectrum for at least one energy level; identifying elements present inthe sample using the EDS spectrum; generating a mesh on a region ofinterest in a SEM image of the sample to locate positions atintersections of the mesh where a depth profile will be taken; gatheringEDS spectra for a plurality of energy levels at a plurality of meshlocations; determining a number of layers of the sample bydistinguishing differences in chemical composition between depths of thesample as beam energies are stepped through; analyzing the chemicalcompositions between adjacent layers in the depth profile to determinewhether a substantial difference exists; and if a substantial differenceexists, generating a depth profile for the area of interest by compilingthe number of layers and the element composition across the mesh.

A system for depth profiling a sample includes a SEM configured to scana sample with an electron beam and at least one energy-dispersive X-rayspectroscopy (EDS) detector to gather EDS spectra for a plurality ofenergy levels to determine element composition and layer interfacesacross an area of interest. A mesh is generated to locate positionswhere a depth profile will be taken. A processor is coupled to the SEMand includes an associated memory. A data reconstruction module isstored in the memory and is configured to gather EDS spectra for aplurality of energy levels at a plurality of mesh locations to determinea number of layers and their composition at each mesh location bydistinguishing differences in chemical composition between depths asbeam energies are stepped through. The data reconstruction module isfurther configured to generate a depth profile for the area of interestby compiling the number of layers and the element composition across themesh.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is a block/flow diagram showing a scanning electron microscope(SEM) system in accordance with the present principles;

FIG. 2 is a cross-section of a sample showing beam penetrationdistributions in accordance with the present principles;

FIG. 3 is a block/flow diagram showing a method for gathering a depthcomposition profile of a sample using a SEM in accordance with oneillustrative embodiment;

FIG. 4 is a block/flow diagram showing a method for generating a depthprofile from energy-dispersive X-ray spectroscopy (EDS) data/spectra fora sample using a SEM in accordance with one illustrative example; and

FIG. 5 is an image of a sample with four positions marked and depthprofiles indicated for each of the four positions in accordance with oneillustrative embodiment.

DETAILED DESCRIPTION

In accordance with the present principles, a scanning electronmicroscope (SEM) is employed to analyze materials to generate across-sectional depth composition into a surface of a sample. This isespecially useful for small samples that are extremely difficult tomanually cross-section and for specimens where non-destructive testingis needed. In one embodiment, a SEM creates a cross-sectional view intothe sample by varying a beam voltage of the SEM. A cross-sectional depthcomposition of a surface is determined by performing a plurality ofpoint scans using a SEM at various beam energy levels and then comparingelectron dispersive X-ray spectroscopy (EDS) results at those variousenergy levels to create a depth composition.

In one illustrative method, beam penetration (which has a tear dropshape) is measured at various beam energy levels. As the beam energy isprogressively increased or decreased, the composition that is measuredby EDS detectors changes. These changes will be employed to determine adepth, shape and/or composition of the layers or structures of thesample.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the blocks may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

It is to be understood that the present invention will be described interms of a given illustrative architecture; however, otherarchitectures, structures, materials and process features and steps maybe varied within the scope of the present invention.

It will also be understood that when an element such as a layer, regionor object is referred to as being “on” or “over” another element, it canbe directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements may be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present principles, as well as other variations thereof, means thata particular feature, structure, characteristic, and so forth describedin connection with the embodiment is included in at least one embodimentof the present principles. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This may be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, an illustrative scanningelectron microscope (SEM) system 10 is shown in accordance with thepresent principles. The SEM system 10 includes a scanning electronmicroscope 12 that produces images 14 of a sample 16 by scanning with afocused beam 18 of electrons. The electrons interact with atoms in thesample and produce signals that include information about a sample'ssurface topography and composition. An electron beam is scanned on aplatform 20 on which the sample 16 is placed and moved. A positionalrelationship of the beam 18 and the information detected from theelectrons to create a detected signal are employed to produce images 14of the sample 16. The SEM 12 can produce an electron beam having anenergy ranging from between about 0.2 keV to 40 keV, although otherenergies may be employed. The beam 18 is focused on the sample 16 by oneor more condenser lenses 15 to a spot on the sample 16. The beam 18 maybe scanned in a raster pattern or any other pattern over an area ofsample 16.

A mesh or grid 26 is projected onto an image 14 or programmed into theplatform 20 or SEM 12 to control motion of the sample 16 and/or electronbeam 18. Intersections of the mesh or grid 26 are locations where thebeam 18 will be parked while energy-dispersive X-ray spectroscopy (EDS)detectors 22 measure scattered X-rays to be analyzed. The X-rayspectroscopy data and position data will be stored in a memory 30 in aprofile data structure 32. The memory 30 is coupled to a processor 40.The processor 40 carries out computations and system functions and maybe employed to control SEM operations. The processor 40 and memory 30may be integrated with the SEM 12 or may be part of an external computersystem or network.

The profile data 32 is employed to identify a composition and structureof the sample 16 at each location. The EDS detector(s) 22 may beemployed in elemental analysis to analyze an intensity and spectrum ofelectron-induced luminescence in the sample 16. This is performed bygathering EDS spectra from the detectors 22 and distinguishingdifferences between chemical compositions as the beam energy isincreased or decreased. The beam energy is controlled relative to a planstored in a beam control module 34. The beam control module 34 mayrandomly select a sequence of beam energies or may follow a determinedprotocol. The plan may be specific to a sample type, different gridlocations or any other criteria. A data construction module 36 maps outthe sample 16 using the data stored in the profile data structure 32.

The data reconstruction module 36, which is stored in the memory 30, isconfigured to gather EDS spectra for a plurality of energy levels at aplurality of mesh locations to determine a number of layers and theircomposition at each mesh location by distinguishing differences inchemical composition between depths as beam energies are steppedthrough. The data reconstruction module 36 is further configured togenerate a depth profile for the area of interest by compiling thenumber of layers and the element composition across the mesh. The depthprofile provides a virtual model of the sample.

The data construction module 36 may generate an image for display on adisplay/interface 42 to show a cross-sectional structure of the sample16 using the EDS spectra signals. The display/interface 42 may includeperipherals, such as a keyboard, mouse, microphone, etc. to enable inputand output (e.g., speakers, display, etc.) for user interaction with thesystem 10.

Referring to FIG. 2 with continued reference to FIG. 1, an illustrativecross-section of a sample 16 is shown in accordance with the presentprinciples. In the illustrative embodiment, the sample includes threelayers: a layer of copper 102, a layer of nickel 104 and a layer of gold106. The layers 102, 104 and 106 may have different depths. A SEMemploys beams having various energies, which range between 5 keV and 20keV in this example.

When a primary electron beam 18 interacts with the sample 16, theelectrons lose energy by repeated random scattering and absorptionwithin a teardrop-shaped volume of the specimen known as an interactionvolume 110, which extends from less than 100 nm to approximately 5 μmbelow a surface 112. The size of the interaction volume 110 depends onthe electron's landing energy, the atomic number of the sample and thedensity of the material. The energy exchange between the electron beam18 and the sample 16 results in the reflection of high-energy electronsby elastic scattering, emission of secondary electrons by inelasticscattering and the emission of electromagnetic radiation (includingX-rays), each of which can be detected by specialized detectorsincluding EDS detectors 22.

The beam current absorbed by the sample 16 can also be detected and usedto create images of the distribution of specimen current. Electronicamplifiers of various types may be employed to amplify the signals,which are displayed as variations in brightness on a computer display42. Each pixel of computer video memory is synchronized with a positionof the beam 18 on the sample 16, and a resulting image is a distributionmap of the intensity of the signal being emitted from the scanned areaof the sample 16 and saved to memory 30 in a profile data structure 36in computer storage.

A beam penetration depth X (μm) can be determined by relating beamenergy E₀ (keV) and material density ρ. A given sample may includemultiple layers of material, and therefore beam penetration will changedepending on sample composition. An equation (1) shows a relationshipbetween beam energy E₀ (keV) and beam penetration depth X (μm) where ρis the density:

X(μm)=(0.1E ₀ ^(1.5))/ρ  (Eq. 1)

In other embodiments, Monte Carlo simulation may be employed todetermine beam penetration in a sample. Monte Carlo simulation modelsscattering paths through the materials and may employ a large populationof scattering particles to map out a scatter profile for the particles.The Monte Carlo simulation results in plots tracing out paths thatcollectively resemble the tear-drop shape of beam penetration 110. Fromthe beam penetration profile, whether computed or simulated, thematerials and structures can be determined for the sample 16.

Referring to FIG. 3, a method for gathering a depth composition profileof a sample using a SEM is shown in accordance with one illustrativeexample. In block 202, an EDS spectrum is gathered at a highest energylevel (e.g., 20 keV, or 40 keV) of interest. The EDS spectrum is takenfrom the entire area of interest. The EDS spectrum is mapped withposition in the area of interest. In block 204, the elements included inthe sample are identified using the EDS spectra. The identified elementsmay be mapped with position in the area of interest. In block 206, amesh or grid is overlaid onto the sample area to be analyzed with EDS.The mesh intersections are where the beam will park to take the EDSspectrum. A resolution of the depth composition will be greater withsmaller mesh size.

In block 208, EDS spectra are gathered at the mesh intersections foreach sequential beam energy level. In a given method, the number of beamenergy levels may be selected based upon knowledge of the sample, thesize of the sample, the number of layers in the sample, etc. In oneembodiment, the number of different energy levels may be three, in otherembodiments, the number of energy levels may be much higher. The energylevels may be incremented or decremented by a discrete amount for eachiteration (e.g., 5 keV).

In block 210, a number of layers in the materials may be determined bydistinguishing substantial differences between chemical compositions ofthe layers as the beam energy increases or decreases. The data profileinformation is stored. In block 212, the profile data is compiled toform a depth profile across the area of interest. The compilation may bedisplayed to be viewed or analyzed. The present principles enablecross-sectioning of samples to determine constituent structures andmaterials, e.g., that are too fragile or too small to deconstruct orcross-section mechanically.

Referring to FIG. 4, a method for generating a depth profile from EDSdata/spectra for a sample using a SEM is shown in accordance with oneillustrative example. In block 302, EDS data from a lowest energy levelscan (of a set of energy levels selected for generating the profile inFIG. 3) is examined, e.g., for the profile data structure. In block 304,a determination is made as to whether EDS data for a higher level scanexists. If no, the data compilation is completed in block 306.Otherwise, if a higher level scan exists, a determination is made inblock 308 as to whether there is a substantial difference in chemicalcomposition. A substantial difference may be measured in accordance withuser defined criteria. In one example, substantial may be determinedbased upon a difference in element or atomic percent of an elementand/or the detection of a previously undetected element.

If there is not a substantial difference in chemical composition, thepath returns to block 304 and continues. If there is a substantialdifference in chemical composition, in block 310, a depth or thicknessof the layer or layers are determined by correlating the known beamenergy with atomic number and/or density of the material(s). The depthis determined at the point where the chemical composition changed, whichprovides an indication where the layer interface exists betweenmaterials of different chemical compositions.

In block 312, the depth or thickness of the layer or layers are storedin a registry or data profile structure. Then, the path returns to block304 to continue through other energy levels for the area of interest.

Referring to FIG. 5, an illustrative example showing a sample 402 havingdifferent cross-section profiles at position 1-4 is shown to demonstratethe present principles. In accordance with the present principles, across-section is generated for the sample 402 including, e.g.,interfaces between different materials using a plurality of differentelectron beam energies as described above. As described, this is usefulwhen the sample is too small to be cross-sectioned mechanically or hasto be preserved (no damage). The sample shown in FIG. 5 is an electricalconnector that has experienced wear (e.g., wear due to one-time orrepeated use over time). Some of the material is abraded away or damagedand some materials is pristine (see positions 1-4). The presentprinciples employ electron beams of varying energies to reconstruct thecross-section of the electrical connector at each position (1-4). Inthis way, the sample can be measured without destruction and mechanicalcross-sectioning is avoided (e.g., no sawing through to cross-sectionthe sample).

Beam penetration depth can be determined by relating beam energy andsample composition as described above, e.g., by equation or Monte Carlosimulation. By calculating or simulating the beam penetration depth andcorrelating the depth with the known compositions at various beamenergies, a cross sectional depth composition can be created. An outputof the depth composition includes layers 102, 104 and 106 at differentpositions 1-4 on the sample 402. The sample 402 is an example showingwear experienced by an electrical connector in an SEM image.

By scanning the positions 1-4 at various beam energies, the presentprinciples are able to generate a depth profile in the wear area ofsample 402. Positions 1-4 in the sample 402 are examples of areas ofinterest in the wear spot. Example depth profiles 404, 406, 408 and 410corresponding with regions 1-4 are shown. Depth profile 404 (position 1)includes no wear and has 30 micro-inches of gold of a top layer 106intact. Depth profile 406 (position 2) shows signs of wear with only 5micro-inches of gold remaining from the top layer 106. Depth profile 408(position 3) has the gold layer 106 completely worn away and only 15micro-inches of a 30 micro-inch nickel layer 104 remaining. Depthprofile 410 (position 4) has the gold layer 106 and nickel layer 104completely worn away, and a copper layer 102 is exposed.

Having described preferred embodiments for cross sectional depthcomposition generation utilizing scanning electron microscopy (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artin light of the above teachings. It is therefore to be understood thatchanges may be made in the particular embodiments disclosed which arewithin the scope of the invention as outlined by the appended claims.Having thus described aspects of the invention, with the details andparticularity required by the patent laws, what is claimed and desiredprotected by Letters Patent is set forth in the appended claims.

What is claimed is:
 1. A system for depth profiling a sample,comprising: an excitation source configured to scan a sample with anexcitation beam; at least one energy detector to gather excitationspectra for a plurality of energy levels to determine elementcomposition and layer interfaces across an area of interest; and a datareconstruction module configured to analyze excitation spectra for aplurality of energy levels at a plurality of locations in the area ofinterest to determine a number of layers and their composition at eachlocation by distinguishing differences in chemical composition betweendepths as beam energies are stepped through, the data reconstructionmodule further configured to generate a depth profile for the area ofinterest by compiling the number of layers and the chemical composition.2. The system as recited in claim 1, wherein the number of beam energiesincluded are stepped through a set step size.
 3. The system as recitedin claim 1, wherein the depth profile is determined by correlating beamenergy with atomic number and/or material density to determine a depthof an interface between materials of different chemical compositions. 4.The system as recited in claim 1, further comprising a profile datastructure for storing information for the depth profile.
 5. The systemas recited in claim 1, wherein the depth profile provides a virtualmodel of the sample.
 6. The system as recited in claim 1, wherein theexcitation source comprises a scanning electron microscope (SEM).
 7. Thesystem as recited in claim 1, wherein the excitation beam comprises anelectron beam.
 8. The system as recited in claim 1, wherein the at leastone energy detector comprises at least one energy dispersive X-rayspectroscopy (EDS) detector.
 9. The system as recited in claim 1,wherein a mesh is generated to determine the plurality of locations inthe area of interest.
 10. The system as recited in claim 1, furthercomprising a display configured to display an image of a cross-sectionalstructure of the sample as a result of the depth profile.
 11. The systemas recited in claim 1, further comprising at least one electronicamplifier configured to detect and amplify current absorbed from theexcitation beam by the sample.
 12. A system for depth profiling asample, comprising: a mesh generated to locate positions where a depthprofile will be taken; a data reconstruction module configured to gatherenergy-dispersive X-ray spectroscopy (EDS) spectra using an appliedelectron beam for a plurality of energy levels at a plurality of meshlocations to determine a number of layers and their composition at eachmesh location as beam energies are varied, the data reconstructionmodule further configured to generate a depth profile for the area ofinterest.
 13. The system as recited in claim 12, wherein the number ofbeam energies included are stepped through a set step size.
 14. Thesystem as recited in claim 12, wherein the depth profile is determinedby correlating beam energy with atomic number and/or material density todetermine a depth of an interface between materials of differentchemical compositions.
 15. The system as recited in claim 12, furthercomprising a profile data structure for storing information for thedepth profile.
 16. The system as recited in claim 12, wherein the depthprofile provides a virtual model of the sample.
 17. The system asrecited in claim 12, wherein the mesh includes a grid size, the gridsize being adjustable such that an adjustment to the grid size controlsa resolution of the depth profile.
 18. The system as recited in claim12, further comprising a display configured to display an image of across-sectional structure of the sample as a result of the depthprofile.
 19. The system as recited in claim 12, further comprising atleast one electronic amplifier configured to detect and amplify currentabsorbed from the excitation beam by the sample.
 20. The system asrecited in claim 12, wherein the data reconstruction module isconfigured to determine the number of layers and their composition usinga Monte Carlo simulation of beam penetration depth.